I actually think it's the opposite, that it matters even more now because of the 4 division and playoff format. There's only 7 teams in our division, 3 teams automatically make it, the other 4 are left fighting for a wild-card spot. I would think that you don't want to trade Ryan O'Reilly to a team in the division where you're battling to get one of the top 3 spots. In the old format, plain and simple top 8 teams make it. But now, divisional hockey matters even more, which is why I wouldn't want to trade within the division unless something huge came back
But what difference does it really make if you think you're getting a player back that helps your team? I don't think you can be a good GM and be scared to make a move because it might help the other team more than yours.
There's good players on every team, it just so happens this one would have a connection to the Avs. O'Reilly can sign within the division in a year and half any way, just like Stastny did. In hindsight, which would be better? Keeping Stastny and letting him walk for St Louis, or trading him to St Louis the summer before he hit UFA and getting a good player back?
In this case, it would be trading him outside of the division for a lesser return and ROR signing in the division a year after, or the Avs trading him within the division for a better return. I'll take the trade within the division. If the return is better outside the division, obviously the point is moot.
It's all the optics of him being an ex Av and potentially hurting the Avs in a couple more games a year than normal, but yo have the player you got in return helping you for potentially 82 games a year. Teams are gonna be good no matter what in the NHL now, there's too much parity. IMO you have to focus only on what makes your team the best, even if it helps the other team.